1. Field of the Invention
The present invention pertains to cardiac revascularization and more particularly to a procedure for cardiac revascularization and related tools for forming a blood flow path through a heart wall from a heart chamber to a coronary vessel.
2. Description of the Prior Art
Commonly assigned and co-pending U.S. patent application Ser. No. 08/882,397 filed Jun. 25, 1997(now issued as U.S. Pat. No. 5,944,019), entitled "Method and Apparatus for Performing Coronary Bypass Surgery", and filed in the name of inventors Mark B. Knudson and William L. Giese, teaches an implant for defining a blood flow conduit directly from a chamber of the heart to a lumen of a coronary vessel. The text of the '397 application has been published on Feb. 25, 1998 in corresponding UK Patent Application GB 2 316 322 A. An embodiment disclosed in the aforementioned application teaches an L-shaped implant in the form of a rigid conduit. The conduit has one leg sized to be received within a lumen of a coronary artery and a second leg sized to pass through the myocardium and extend into the left ventricle of the heart. As disclosed in the above-referenced application, the conduit is rigid and remains open for blood flow to pass through the conduit during both systole and diastole. The conduit penetrates into the left ventricle in order to prevent tissue growth and occlusions over an opening of the conduit.
Commonly assigned and co-pending U.S. patent application Ser. No. 08/944,313 filed Oct. 6, 1997(now issued as U.S. Pat. No. 5,984,956), entitled "Transmyocardial Implant", and filed in the name of inventors Katherine S. Tweden, Guy P. Vanney and Thomas L. Odland, teaches an implant such as that shown in the aforementioned '397 application with an enhanced fixation structure. One embodiment of the enhanced fixation structure includes a fabric surrounding at least a portion of the conduit to facilitate tissue growth on the exterior of the implant.
Implants such as those shown in the aforementioned applications include a portion to be placed within a coronary vessel and a portion to be placed within the myocardium. When placing an implant in the myocardium, a hole is formed through the heart wall into the left ventricle. As a result, blood may flow out of the left ventricle through the formed hole or through the implant after insertion through the myocardium. In addition to undesirable blood loss, the uncontrolled flow of blood can obscure a surgeon's field of vision.
When placing a portion of the implant in the coronary artery or other coronary vessel, the artery is incised by an amount sufficient to insert the implant. Preferably, the artery is ligated distal to an obstruction. A transverse incision is made through the artery distal to the ligation. Such an incision results in a contraction of the coronary vessel to a size substantially smaller than the implant. Therefore, it is difficult to insert the implant into the lumen of the coronary vessel. Such vessels are elastic and can be urged to an expanded shape sufficient to fit over the implant. However, due to the small size of the vessel, restricted space for manipulating surgical tools, and the importance of avoiding damage to the coronary vessel, such a manipulation of the vessel is difficult. Also, it is desirable to be able to insert the implant within the vessel as rapidly as possible to minimize the amount of time during which blood flow through the vessel is interrupted.